1. Field of the Art
The present invention relates in general to a hydraulic braking device or system for an automotive vehicle, and more particularly to such a hydraulic braking system having anti-skid pressure control means for controlling the braking pressure in wheel brake cylinders in order to prevent an excessive slip of the vehicle wheels on the road surface upon brake application.
2. Related Art Statement
An example of such a hydraulic braking system for an automotive vehicle is known, according to Japanese Patent Application laid open in 1981 under Publication No. 56-142733, which comprises: (a) a master cylinder for generating a fluid pressure in response to an operation of a manually-operated member; (b) a brake having a brake cylinder actuated by the fluid pressure generated by the master cylinder, for restraining the rotation of a drive wheel of the vehicle; (c) a primary fluid passage connecting the master cylinder and the brake cylinder to feed a brake fluid from the master cylinder to the brake cylinder; (d) a solenoid valve disposed in the primary fluid passage and selectively placed in one of a first operating position for communication of the brake cylinder with the master cylinder, and a second operating position for communication of the brake cylinder with a reservoir, the solenoid valve being switched between the first and second operating positions under the control of a controller, to control a level of a braking pressure in the brake cylinder for preventing an excessive amount of slip of the drive wheel on the road surface upon brake application; (e) a pump for pumping the brake fluid from the reservoir and returning the pumped fluid via a pump passage to the primary fluid passage at a point thereof between the master cylinder and the solenoid valve; (f) a check valve disposed in a portion of the primary fluid passage between the master cylinder and the above-identified point, the check valve being closed to prevent a flow of the brake fluid therethrough in a direction from the pump toward the master cylinder when the pressure on one side of the check valve on the side of the pump is higher than that on the other side on the side of the master cylinder, whereby the check valve serves as a shut-off valve for the master cylinder; and (g) an accumulator disposed in a fluid passage connecting the pump and the solenoid valve, the accumulator having a housing, a piston slidably received in the housing, and biasing means for biasing the piston axially in one direction, the piston cooperating with the housing to define a storage chamber of a variable volume in which the brake fluid is stored under a relatively high pressure.
The hydraulic braking system with anti-skid pressure control means constructed as described above, prevents a so-called "kick-back" phenomenon of a brake pedal or other manually-operated member, which is conventionally encountered due to a return flow of the brake fluid from the pump to the primary fluid passage, and then into the master cylinder. The elimination of the "kick-back" phenomenon leads to an improved operating feel of the brake pedal.